Recent content by CCC

Whoops, reading it I realized I didn't say quite what I meant - not that fewer particles collide with the pipe, but that the angles of the collision become smaller and smaller.

Thinking of individual fluid particles, my guess is that the "force" is simply particles backing up somewhat at the constriction point and contributing a higher proportion of collisions on particles ahead of them in a direction down the pipe. As the average movement of the particles is directed...